Airbags for motor vehicles have become ubiquitous in passenger vehicles. These airbags are installed at strategic points in the passenger compartment of a vehicle and, in the event of a collision, are rapidly inflated with gas so that they act as an energy absorbing barrier between the vehicle occupant and an interior surface of the passenger compartment (e.g., steering wheel, dashboard, or windows). For example, side curtain airbags typically are installed within one or more of the pillars of the vehicle so that they provide protection during roll-over or side impact collisions. With the advent of such airbags, manufacturers began coating the airbag fabric to modify the gas permeability of the fabric, enabling the airbags manufactured from the fabric to stay inflated for longer periods of time and provided the needed protection during the collision event.
There are many types of coating compositions used to produce such coated fabrics, but one class of coating composition that is quite popular is a dispersion of a polymer in a suitable medium (e.g., aqueous medium). And while these dispersion-based systems are popular, they are not free from drawbacks and difficulties. For example, the polymer must be fairly evenly dispersed within the coating composition in order to produce a coating on the fabric that is of good and consistent quality. The addition of additives (e.g., pigments, fillers, flame retardants, etc.) to such a dispersion can adversely affect the rheology of the dispersion, making it more difficult to produce a coating on the fabric that is of good and consistent quality. Furthermore, particulate additives can be difficult to evenly disperse within the coating composition; and unevenly dispersed particulates in the coating composition will adversely affect the quality of the coating on the fabric. To improve the quality of the dispersion (of both polymer and particulate additives), some have advocated the use of coalescing solvents (e.g., N-methylpyrrolidone). However, the use of coalescing solvents presents its own set of potential problems. For example, the coalescing solvents typically have boiling points that are high enough that they are left behind in the coating on the airbag fabric. But the boiling point of the coalescing solvent is sufficiently low that, once the airbag is installed in a vehicle, the coalescing solvent can begin to volatilize and be released into the passenger compartment of the vehicle.
In view of the foregoing, it can be seen that a need remains for coating compositions and coated airbag fabrics that can meet the demanding needs of the automotive airbag industry while addressing some of the problems inherent in current coating compositions and coated fabrics. Applicants believe that the coating composition and coated airbag described in the present application meet this need.